path: root/src/core/core-varlink.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include "core-varlink.h"
#include "mkdir-label.h"
#include "strv.h"
#include "user-util.h"
#include "varlink.h"
#include "varlink-io.systemd.UserDatabase.h"
#include "varlink-io.systemd.ManagedOOM.h"

typedef struct LookupParameters {
        const char *user_name;
        const char *group_name;
        union {
                uid_t uid;
                gid_t gid;
        };
        const char *service;
} LookupParameters;

static const char* const managed_oom_mode_properties[] = {
        "ManagedOOMSwap",
        "ManagedOOMMemoryPressure",
};

static int build_user_json(const char *user_name, uid_t uid, JsonVariant **ret) {
        assert(user_name);
        assert(uid_is_valid(uid));
        assert(ret);

        return json_build(ret, JSON_BUILD_OBJECT(
                                   JSON_BUILD_PAIR("record", JSON_BUILD_OBJECT(
                                       JSON_BUILD_PAIR("userName", JSON_BUILD_STRING(user_name)),
                                       JSON_BUILD_PAIR("uid", JSON_BUILD_UNSIGNED(uid)),
                                       JSON_BUILD_PAIR("gid", JSON_BUILD_UNSIGNED(uid)),
                                       JSON_BUILD_PAIR("realName", JSON_BUILD_CONST_STRING("Dynamic User")),
                                       JSON_BUILD_PAIR("homeDirectory", JSON_BUILD_CONST_STRING("/")),
                                       JSON_BUILD_PAIR("shell", JSON_BUILD_CONST_STRING(NOLOGIN)),
                                       JSON_BUILD_PAIR("locked", JSON_BUILD_BOOLEAN(true)),
                                       JSON_BUILD_PAIR("service", JSON_BUILD_CONST_STRING("io.systemd.DynamicUser")),
                                       JSON_BUILD_PAIR("disposition", JSON_BUILD_CONST_STRING("dynamic"))))));
}

static bool user_match_lookup_parameters(LookupParameters *p, const char *name, uid_t uid) {
        assert(p);

        if (p->user_name && !streq(name, p->user_name))
                return false;

        if (uid_is_valid(p->uid) && uid != p->uid)
                return false;

        return true;
}

static int build_managed_oom_json_array_element(Unit *u, const char *property, JsonVariant **ret_v) {
        bool use_limit = false;
        CGroupContext *c;
        const char *mode;

        assert(u);
        assert(property);
        assert(ret_v);

        if (!UNIT_VTABLE(u)->can_set_managed_oom)
                return -EOPNOTSUPP;

        c = unit_get_cgroup_context(u);
        if (!c)
                return -EINVAL;

        if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(u)))
                /* systemd-oomd should always treat inactive units as though they didn't enable any action since they
                 * should not have a valid cgroup */
                mode = managed_oom_mode_to_string(MANAGED_OOM_AUTO);
        else if (streq(property, "ManagedOOMSwap"))
                mode = managed_oom_mode_to_string(c->moom_swap);
        else if (streq(property, "ManagedOOMMemoryPressure")) {
                mode = managed_oom_mode_to_string(c->moom_mem_pressure);
                use_limit = true;
        } else
                return -EINVAL;

        return json_build(ret_v, JSON_BUILD_OBJECT(
                                 JSON_BUILD_PAIR("mode", JSON_BUILD_STRING(mode)),
                                 JSON_BUILD_PAIR("path", JSON_BUILD_STRING(u->cgroup_path)),
                                 JSON_BUILD_PAIR("property", JSON_BUILD_STRING(property)),
                                 JSON_BUILD_PAIR_CONDITION(use_limit, "limit", JSON_BUILD_UNSIGNED(c->moom_mem_pressure_limit))));
}

int manager_varlink_send_managed_oom_update(Unit *u) {
        _cleanup_(json_variant_unrefp) JsonVariant *arr = NULL, *v = NULL;
        CGroupContext *c;
        int r;

        assert(u);

        if (!UNIT_VTABLE(u)->can_set_managed_oom || !u->manager || !u->cgroup_path)
                return 0;

        if (MANAGER_IS_SYSTEM(u->manager)) {
                /* In system mode we can't send any notifications unless oomd connected back to us. In this
                 * mode oomd must initiate communication, not us. */
                if (!u->manager->managed_oom_varlink)
                        return 0;
        } else {
                /* If we are in user mode, let's connect to oomd if we aren't connected yet. In this mode we
                 * must initiate communication to oomd, not the other way round. */
                r = manager_varlink_init(u->manager);
                if (r <= 0)
                        return r;
        }

        c = unit_get_cgroup_context(u);
        if (!c)
                return 0;

        r = json_build(&arr, JSON_BUILD_EMPTY_ARRAY);
        if (r < 0)
                return r;

        for (size_t i = 0; i < ELEMENTSOF(managed_oom_mode_properties); i++) {
                _cleanup_(json_variant_unrefp) JsonVariant *e = NULL;

                r = build_managed_oom_json_array_element(u, managed_oom_mode_properties[i], &e);
                if (r < 0)
                        return r;

                r = json_variant_append_array(&arr, e);
                if (r < 0)
                        return r;
        }

        r = json_build(&v, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("cgroups", JSON_BUILD_VARIANT(arr))));
        if (r < 0)
                return r;

        if (MANAGER_IS_SYSTEM(u->manager))
                /* in system mode, oomd is our client, thus send out notifications as replies to the
                 * initiating method call from them. */
                r = varlink_notify(u->manager->managed_oom_varlink, v);
        else
                /* in user mode, we are oomd's client, thus send out notifications as method calls that do
                 * not expect a reply. */
                r = varlink_send(u->manager->managed_oom_varlink, "io.systemd.oom.ReportManagedOOMCGroups", v);

        return r;
}

static int build_managed_oom_cgroups_json(Manager *m, JsonVariant **ret) {
        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *arr = NULL;
        int r;

        assert(m);
        assert(ret);

        r = json_build(&arr, JSON_BUILD_EMPTY_ARRAY);
        if (r < 0)
                return r;

        for (UnitType t = 0; t < _UNIT_TYPE_MAX; t++) {

                if (!unit_vtable[t]->can_set_managed_oom)
                        continue;

                LIST_FOREACH(units_by_type, u, m->units_by_type[t]) {
                        CGroupContext *c;

                        if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(u)))
                                continue;

                        c = unit_get_cgroup_context(u);
                        if (!c)
                                continue;

                        for (size_t j = 0; j < ELEMENTSOF(managed_oom_mode_properties); j++) {
                                _cleanup_(json_variant_unrefp) JsonVariant *e = NULL;

                                /* For the initial varlink call we only care about units that enabled (i.e. mode is not
                                 * set to "auto") oomd properties. */
                                if (!(streq(managed_oom_mode_properties[j], "ManagedOOMSwap") && c->moom_swap == MANAGED_OOM_KILL) &&
                                    !(streq(managed_oom_mode_properties[j], "ManagedOOMMemoryPressure") && c->moom_mem_pressure == MANAGED_OOM_KILL))
                                        continue;

                                r = build_managed_oom_json_array_element(u, managed_oom_mode_properties[j], &e);
                                if (r < 0)
                                        return r;

                                r = json_variant_append_array(&arr, e);
                                if (r < 0)
                                        return r;
                        }
                }
        }

        r = json_build(&v, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("cgroups", JSON_BUILD_VARIANT(arr))));
        if (r < 0)
                return r;

        *ret = TAKE_PTR(v);
        return 0;
}

static int vl_method_subscribe_managed_oom_cgroups(
                Varlink *link,
                JsonVariant *parameters,
                VarlinkMethodFlags flags,
                void *userdata) {

        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
        Manager *m = ASSERT_PTR(userdata);
        pid_t pid;
        Unit *u;
        int r;

        assert(link);

        r = varlink_get_peer_pid(link, &pid);
        if (r < 0)
                return r;

        u = manager_get_unit_by_pid(m, pid);
        if (!u)
                return varlink_error(link, VARLINK_ERROR_PERMISSION_DENIED, NULL);

        /* This is meant to be a deterrent and not actual security. The alternative is to check for the systemd-oom
         * user that this unit runs as, but NSS lookups are blocking and not allowed from PID 1. */
        if (!streq(u->id, "systemd-oomd.service"))
                return varlink_error(link, VARLINK_ERROR_PERMISSION_DENIED, NULL);

        if (json_variant_elements(parameters) > 0)
                return varlink_error_invalid_parameter(link, parameters);

        /* We only take one subscriber for this method so return an error if there's already an existing one.
         * This shouldn't happen since systemd-oomd is the only client of this method. */
        if (FLAGS_SET(flags, VARLINK_METHOD_MORE) && m->managed_oom_varlink)
                return varlink_error(link, "io.systemd.ManagedOOM.SubscriptionTaken", NULL);

        r = build_managed_oom_cgroups_json(m, &v);
        if (r < 0)
                return r;

        if (!FLAGS_SET(flags, VARLINK_METHOD_MORE))
                return varlink_reply(link, v);

        assert(!m->managed_oom_varlink);
        m->managed_oom_varlink = varlink_ref(link);
        return varlink_notify(m->managed_oom_varlink, v);
}

static int manager_varlink_send_managed_oom_initial(Manager *m) {
        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
        int r;

        assert(m);

        if (MANAGER_IS_SYSTEM(m))
                return 0;

        assert(m->managed_oom_varlink);

        r = build_managed_oom_cgroups_json(m, &v);
        if (r < 0)
                return r;

        return varlink_send(m->managed_oom_varlink, "io.systemd.oom.ReportManagedOOMCGroups", v);
}

static int vl_method_get_user_record(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {

        static const JsonDispatch dispatch_table[] = {
                { "uid",      JSON_VARIANT_UNSIGNED, json_dispatch_uid_gid,      offsetof(LookupParameters, uid),       0         },
                { "userName", JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, user_name), JSON_SAFE },
                { "service",  JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, service),   0         },
                {}
        };

        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
        LookupParameters p = {
                .uid = UID_INVALID,
        };
        _cleanup_free_ char *found_name = NULL;
        uid_t found_uid = UID_INVALID, uid;
        Manager *m = ASSERT_PTR(userdata);
        const char *un;
        int r;

        assert(parameters);

        r = varlink_dispatch(link, parameters, dispatch_table, &p);
        if (r != 0)
                return r;

        if (!streq_ptr(p.service, "io.systemd.DynamicUser"))
                return varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);

        if (uid_is_valid(p.uid))
                r = dynamic_user_lookup_uid(m, p.uid, &found_name);
        else if (p.user_name)
                r = dynamic_user_lookup_name(m, p.user_name, &found_uid);
        else {
                DynamicUser *d;

                HASHMAP_FOREACH(d, m->dynamic_users) {
                        r = dynamic_user_current(d, &uid);
                        if (r == -EAGAIN) /* not realized yet? */
                                continue;
                        if (r < 0)
                                return r;

                        if (!user_match_lookup_parameters(&p, d->name, uid))
                                continue;

                        if (v) {
                                r = varlink_notify(link, v);
                                if (r < 0)
                                        return r;

                                v = json_variant_unref(v);
                        }

                        r = build_user_json(d->name, uid, &v);
                        if (r < 0)
                                return r;
                }

                if (!v)
                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);

                return varlink_reply(link, v);
        }
        if (r == -ESRCH)
                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
        if (r < 0)
                return r;

        uid = uid_is_valid(found_uid) ? found_uid : p.uid;
        un = found_name ?: p.user_name;

        if (!user_match_lookup_parameters(&p, un, uid))
                return varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL);

        r = build_user_json(un, uid, &v);
        if (r < 0)
                return r;

        return varlink_reply(link, v);
}

static int build_group_json(const char *group_name, gid_t gid, JsonVariant **ret) {
        assert(group_name);
        assert(gid_is_valid(gid));
        assert(ret);

        return json_build(ret, JSON_BUILD_OBJECT(
                                   JSON_BUILD_PAIR("record", JSON_BUILD_OBJECT(
                                       JSON_BUILD_PAIR("groupName", JSON_BUILD_STRING(group_name)),
                                       JSON_BUILD_PAIR("description", JSON_BUILD_CONST_STRING("Dynamic Group")),
                                       JSON_BUILD_PAIR("gid", JSON_BUILD_UNSIGNED(gid)),
                                       JSON_BUILD_PAIR("service", JSON_BUILD_CONST_STRING("io.systemd.DynamicUser")),
                                       JSON_BUILD_PAIR("disposition", JSON_BUILD_CONST_STRING("dynamic"))))));
    }

static bool group_match_lookup_parameters(LookupParameters *p, const char *name, gid_t gid) {
        assert(p);

        if (p->group_name && !streq(name, p->group_name))
                return false;

        if (gid_is_valid(p->gid) && gid != p->gid)
                return false;

        return true;
}

static int vl_method_get_group_record(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {

        static const JsonDispatch dispatch_table[] = {
                { "gid",       JSON_VARIANT_UNSIGNED, json_dispatch_uid_gid,      offsetof(LookupParameters, gid),        0         },
                { "groupName", JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, group_name), JSON_SAFE },
                { "service",   JSON_VARIANT_STRING,   json_dispatch_const_string, offsetof(LookupParameters, service),    0         },
                {}
        };

        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
        LookupParameters p = {
                .gid = GID_INVALID,
        };
        _cleanup_free_ char *found_name = NULL;
        uid_t found_gid = GID_INVALID, gid;
        Manager *m = ASSERT_PTR(userdata);
        const char *gn;
        int r;

        assert(parameters);

        r = varlink_dispatch(link, parameters, dispatch_table, &p);
        if (r != 0)
                return r;

        if (!streq_ptr(p.service, "io.systemd.DynamicUser"))
                return varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);

        if (gid_is_valid(p.gid))
                r = dynamic_user_lookup_uid(m, (uid_t) p.gid, &found_name);
        else if (p.group_name)
                r = dynamic_user_lookup_name(m, p.group_name, (uid_t*) &found_gid);
        else {
                DynamicUser *d;

                HASHMAP_FOREACH(d, m->dynamic_users) {
                        uid_t uid;

                        r = dynamic_user_current(d, &uid);
                        if (r == -EAGAIN)
                                continue;
                        if (r < 0)
                                return r;

                        if (!group_match_lookup_parameters(&p, d->name, (gid_t) uid))
                                continue;

                        if (v) {
                                r = varlink_notify(link, v);
                                if (r < 0)
                                        return r;

                                v = json_variant_unref(v);
                        }

                        r = build_group_json(d->name, (gid_t) uid, &v);
                        if (r < 0)
                                return r;
                }

                if (!v)
                        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);

                return varlink_reply(link, v);
        }
        if (r == -ESRCH)
                return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
        if (r < 0)
                return r;

        gid = gid_is_valid(found_gid) ? found_gid : p.gid;
        gn = found_name ?: p.group_name;

        if (!group_match_lookup_parameters(&p, gn, gid))
                return varlink_error(link, "io.systemd.UserDatabase.ConflictingRecordFound", NULL);

        r = build_group_json(gn, gid, &v);
        if (r < 0)
                return r;

        return varlink_reply(link, v);
}

static int vl_method_get_memberships(Varlink *link, JsonVariant *parameters, VarlinkMethodFlags flags, void *userdata) {

        static const JsonDispatch dispatch_table[] = {
                { "userName",  JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, user_name),  JSON_SAFE },
                { "groupName", JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, group_name), JSON_SAFE },
                { "service",   JSON_VARIANT_STRING, json_dispatch_const_string, offsetof(LookupParameters, service),    0         },
                {}
        };

        LookupParameters p = {};
        int r;

        assert(parameters);

        r = varlink_dispatch(link, parameters, dispatch_table, &p);
        if (r != 0)
                return r;

        if (!streq_ptr(p.service, "io.systemd.DynamicUser"))
                return varlink_error(link, "io.systemd.UserDatabase.BadService", NULL);

        /* We don't support auxiliary groups with dynamic users. */
        return varlink_error(link, "io.systemd.UserDatabase.NoRecordFound", NULL);
}

static void vl_disconnect(VarlinkServer *s, Varlink *link, void *userdata) {
        Manager *m = ASSERT_PTR(userdata);

        assert(s);
        assert(link);

        if (link == m->managed_oom_varlink)
                m->managed_oom_varlink = varlink_unref(link);
}

static int manager_varlink_init_system(Manager *m) {
        _cleanup_(varlink_server_unrefp) VarlinkServer *s = NULL;
        int r;

        assert(m);

        if (m->varlink_server)
                return 1;

        if (!MANAGER_IS_SYSTEM(m))
                return 0;

        r = manager_setup_varlink_server(m, &s);
        if (r < 0)
                return log_error_errno(r, "Failed to set up varlink server: %m");

        if (!MANAGER_IS_TEST_RUN(m)) {
                (void) mkdir_p_label("/run/systemd/userdb", 0755);

                FOREACH_STRING(address, "/run/systemd/userdb/io.systemd.DynamicUser", VARLINK_ADDR_PATH_MANAGED_OOM_SYSTEM) {
                        if (MANAGER_IS_RELOADING(m)) {
                                /* If manager is reloading, we skip listening on existing addresses, since
                                 * the fd should be acquired later through deserialization. */
                                if (access(address, F_OK) >= 0)
                                        continue;
                                if (errno != ENOENT)
                                        return log_error_errno(errno,
                                                               "Failed to check if varlink socket '%s' exists: %m", address);
                        }

                        r = varlink_server_listen_address(s, address, 0666);
                        if (r < 0)
                                return log_error_errno(r, "Failed to bind to varlink socket '%s': %m", address);
                }
        }

        r = varlink_server_attach_event(s, m->event, SD_EVENT_PRIORITY_NORMAL);
        if (r < 0)
                return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");

        m->varlink_server = TAKE_PTR(s);
        return 1;
}

static int vl_reply(Varlink *link, JsonVariant *parameters, const char *error_id, VarlinkReplyFlags flags, void *userdata) {
        Manager *m = ASSERT_PTR(userdata);
        int r;

        if (error_id)
                log_debug("varlink systemd-oomd client error: %s", error_id);

        if (FLAGS_SET(flags, VARLINK_REPLY_ERROR) && FLAGS_SET(flags, VARLINK_REPLY_LOCAL)) {
                /* Varlink connection was closed, likely because of systemd-oomd restart. Let's try to
                 * reconnect and send the initial ManagedOOM update again. */

                m->managed_oom_varlink = varlink_unref(link);

                log_debug("Reconnecting to %s", VARLINK_ADDR_PATH_MANAGED_OOM_USER);

                r = manager_varlink_init(m);
                if (r <= 0)
                        return r;
        }

        return 0;
}

static int manager_varlink_init_user(Manager *m) {
        _cleanup_(varlink_close_unrefp) Varlink *link = NULL;
        int r;

        assert(m);

        if (m->managed_oom_varlink)
                return 1;

        if (MANAGER_IS_TEST_RUN(m))
                return 0;

        r = varlink_connect_address(&link, VARLINK_ADDR_PATH_MANAGED_OOM_USER);
        if (r < 0) {
                if (r == -ENOENT || ERRNO_IS_DISCONNECT(r)) {
                        log_debug("systemd-oomd varlink unix socket not found, skipping user manager varlink setup");
                        return 0;
                }
                return log_error_errno(r, "Failed to connect to %s: %m", VARLINK_ADDR_PATH_MANAGED_OOM_USER);
        }

        varlink_set_userdata(link, m);

        r = varlink_bind_reply(link, vl_reply);
        if (r < 0)
                return r;

        r = varlink_attach_event(link, m->event, SD_EVENT_PRIORITY_NORMAL);
        if (r < 0)
                return log_error_errno(r, "Failed to attach varlink connection to event loop: %m");

        m->managed_oom_varlink = TAKE_PTR(link);

        /* Queue the initial ManagedOOM update. */
        (void) manager_varlink_send_managed_oom_initial(m);

        return 1;
}

int manager_setup_varlink_server(Manager *m, VarlinkServer **ret) {
        _cleanup_(varlink_server_unrefp) VarlinkServer *s = NULL;
        int r;

        assert(m);
        assert(ret);

        r = varlink_server_new(&s, VARLINK_SERVER_ACCOUNT_UID|VARLINK_SERVER_INHERIT_USERDATA);
        if (r < 0)
                return log_debug_errno(r, "Failed to allocate varlink server object: %m");

        varlink_server_set_userdata(s, m);

        r = varlink_server_add_interface_many(
                        s,
                        &vl_interface_io_systemd_UserDatabase,
                        &vl_interface_io_systemd_ManagedOOM);
        if (r < 0)
                return log_error_errno(r, "Failed to add interfaces to varlink server: %m");

        r = varlink_server_bind_method_many(
                        s,
                        "io.systemd.UserDatabase.GetUserRecord",  vl_method_get_user_record,
                        "io.systemd.UserDatabase.GetGroupRecord", vl_method_get_group_record,
                        "io.systemd.UserDatabase.GetMemberships", vl_method_get_memberships,
                        "io.systemd.ManagedOOM.SubscribeManagedOOMCGroups",  vl_method_subscribe_managed_oom_cgroups);
        if (r < 0)
                return log_debug_errno(r, "Failed to register varlink methods: %m");

        r = varlink_server_bind_disconnect(s, vl_disconnect);
        if (r < 0)
                return log_debug_errno(r, "Failed to register varlink disconnect handler: %m");

        *ret = TAKE_PTR(s);
        return 0;
}

int manager_varlink_init(Manager *m) {
        return MANAGER_IS_SYSTEM(m) ? manager_varlink_init_system(m) : manager_varlink_init_user(m);
}

void manager_varlink_done(Manager *m) {
        assert(m);

        /* Explicitly close the varlink connection to oomd. Note we first take the varlink connection out of
         * the manager, and only then disconnect it — in two steps – so that we don't end up accidentally
         * unreffing it twice. After all, closing the connection might cause the disconnect handler we
         * installed (vl_disconnect() above) to be called, where we will unref it too. */
        varlink_close_unref(TAKE_PTR(m->managed_oom_varlink));

        m->varlink_server = varlink_server_unref(m->varlink_server);
        m->managed_oom_varlink = varlink_close_unref(m->managed_oom_varlink);
}